The advantages of electronic lock systems over their mechanical counterparts are obvious in that the electronic lock systems offer greater protection in guarding against unauthorized entry, key duplication and lock picking. The prior art electronic lock systems, in general, include an electronic control circuit which responds to a coded card, or other coded key, to operate an electromechanical latch. The cards in the prior art systems are usually coded optically, magnetically, electrostatically, or capacitively.
U.S. Pat. No. 3,821,704 discloses an electronic lock system in which the electronic control circuit in each door can be readily changed to respond to new codes. This is an essential requirement in hotels, in order that each new guest may be issued a card bearing a new code which will be effective to open a particular door, and which will cause the card issued to the previous guest to be no longer effective in operating the door. A feature in the system described in the patent is that when the new guest inserts his card into the slot in the door of the room assigned to him, the insertion causes the unit in the door to be changed to respond to the new code encoded into the card of the new guest, and to be no longer responsive to the code encoded into the card issued to the previous guest.
As mentioned in U.S. Pat. No. 3,821,704, a requirement in adapting electronic lock systems to hotels is the necessity that the lock must be responsive to a variety of coded cards. For example, a maid must be provided with a maid's card. For security reasons, however, it is generally desirable to provide the maid with a card which will open only the rooms to which the particular maid is assigned, and no others. A supervisor may be issued a higher level master card which will open a larger number of rooms than the maid's card, corresponding to the number of rooms assigned to all maids under the supervision of the supervisor. Still higher level master cards may be issued to hotel personnel for opening all doors in a section of the hotel for maintenance purposes, or in case of fire, or other emergency. It will be seen, therefore, that the requirement of a number of levels of cards, and the recurrent need to change the individual door locks or groups of door locks to control theft, presents a substantial problem in adapting electronic lock systems to hotels.
In the electronic lock system described in the aforesaid patent, each lock is controlled by a decoding device which includes a resettable memory. In its simplest form, the memory is pre-set with a multi-bit combination. Each time a card is used in the system described in the patent, at least two numbers are entered into the system, a key number and an authorization number. If the key number is found to match the combination previously stored in the particular decoding device, the lock of the corresponding door will be activated. If such a match is not made, a comparison is then made between the authorization number on the card and an authorization number entered by the previous user. If the comparison is established, the decoding device is reset to the new key number, so that the lock may be opened by the new card. Accordingly, to change a lock combination in any particular decoding device in any particular door in the system described in the patent, all that is necessary is to encode a newly issued card with a new card number and with the last card authorization number. Then, when the new card is inserted into the particular door, the circuitry will respond to change the stored code to the new code, and to activate the electromechanical latch system to open the door.
In the system described in the patent, when a guest registers for a room, he is given a card bearing at least two fields of encoded information. One field contains the new key number, and the second field contains the authorization number assigned to the last guest to use the room. Upon the first insertion of the card by the new guest, the lock is automatically re-keyed to the new combination encoded into the new card. Thereafter, until the lock combination is again changed, the only card number that will open the particular door is that assigned to the present guest; and no prior guest cards will open the lock since the decoding circuit now contains a new code number.
Because the lock combination is stored in a memory accessible only by a particular logic circuit, electronic door locks of the type described in the patent are not susceptible to being picked. Further, each lock may be re-keyed without the intervention of anyone but the user. Finally, there is no interconnection with a central controller from the individual electronic units in the individual doors, which saves a considerable amount of installation cost.
The electronic lock system of the present invention is of the same general type as described in U.S. Pat. No. 3,821,704. However, the electronic lock system of the invention has additional features which include, inter alia, the installation in each door of a battery energized microcomputer controlled electronic circuit, and which are constructed so that units of the present invention may be installed easily and expeditiously in existing hotel doors of the type having mortise locks or having locks located in the knobs.
Each of the units of the invention mounted in the individual doors responds to a programmable magnetically coded key card which serves to activate an electronic lock circuit if the code is proper, and also to up-date the code stored in the unit if the card has been issued to a new guest. Each unit, in accordance with the concepts of the present invention, is also capable of identifying and recording the time of all entries into the room, and of limiting the number of days the card issued to any particular guest is effective.
The key cards used in the electronic lock system of the invention are magnetically encoded, and they are reprogrammable and may be used many times. Data on each card is proximity sensed by a non-contact electromagnetic read head, when the key card is inserted into a slot in any one of the electronic lock door units, so that the read head does not contact the magnetic material in the card and the problems of ambiguous data transfer due to dust, dirt, grease and the like, are eliminated, such problems being common to the prior art key card reading systems, whether magnetic strip, optical or capacitance encoding of the individual cards is used. In addition, the individual bits on the card used in the system of the invention are sufficiently loosely packed so that the information may be written into the card and read from the card by manual movement of the card without any need for drive motors or the like.
For convenience, each unit may be constructed so that the key cards may be inserted into the slot with either face up. The card may also be programmed with a guest's identity and sent to the guest when a reservation is made. Then, upon entering the hotel, the guest need merely insert his card into a card reader to complete check-in and to receive his room assignment. On check-out the guest merely inserts his card into the reader and his billing information is automatically recorded and he is provided with a print-out.
A portable computer is provided which may be hand carried to any door and plugged into the electronic control unit in that door to read identification and time data stored in the unit, and also to re-program the door unit if necessary, and to program the unit door for an initial use.